One of my favs was from SG1 "The Fifth Race". It might not be as polised as some of the speaches listed, comming from Jack O'Neill, but it comes from the heart
O'Neill: "Look....I don't want to sound ungrateful because I really REALLY appricate you getting that stuff out of my head. But you folkes should understand...that we're out there, NOW. And we might not be ready for a lot of this stuff...but we're doing the best we can....we are a very...curious...race."
*Asgard look at each other for a second...then one offers his hand to Jack*
Asgard: "You have already taken the first steps towards becoming...The Fifth Race"
And while its not technicaly Sci Fi, LOTR, ROTK. Theodon is by far the BEST non main cast character (and even then I would put him as better then several).
Théoden: "Arise!! Arise, Riders of Théoden!! "
"Spears shall be shaken!! Shields shall be splintered! A sword day!! A red day!! Ere the sun rises!!"
*shot of the riders lowering their lances as the music starts to build up.
*Théodenrides down the line, crossing swords with his men*
Théoden: "Ride now! Ride now! Riiiiide! Ride for ruin, and the world's end-ing!!!!"
*turns to face the Orcs and starts screaming*
Théoden: "Deeeeath! "
Riders: "DEEEATH!"
Théoden: "DEEEATH!"
Riders: "
DDDEEEATTTHHHH!!"
Théoden:
DDDEEEATTHHH!!!"
Riders & Heros: "
DDDEEEATTHHH!!"
Théoden: "
FORTH EORLINGAS!
*horns sound the charge and with a roar, the entire host moves into a gallop, then as the music builds up, they charge into the Orcs right flank like a frigen freight train*